Method and arrangement for controlling a rock drilling apparatus

Abstract

The invention relates to a method and an arrangement for adjusting the percussion and the feed of a rock drilling apparatus with respect to each other. In the method, the volume flow of pressure fluid to be supplied to a percussion device (7) and a feed motor (8) is adjusted on the basis of the feed pressure of the feed motor (11), a volume flow adjusted pump (1) being controlled so that the ratio of the pressure applied to the persussion device (7) to the pressure of the feed motor (11) is set by control valves (10, 14). In the arrangement, pressure fluid is supplied to the percussion device (7) and the feed motor (11) by means of a volume flow adjusted pump (1). The arrangement further comprises control valves (10, 14) by means of which the volume flow of the pressure fluid fed by the pump (1) is kept such that the ratio of the pressure of the percussion device and that of the feed motor (11) remains substantially constant.

What is claimed is: 
     
       1. A method of controlling the percussion power of a percussion device in a pressure fluid operated rock drilling apparatus, including a pressure reduction means and feed device, comprising the steps of: (i) supplying a pressure fluid simultaneously to the percussion device and through the pressure reduction means to the feed device;   (ii) controlling the percussion power by adjusting the pressure of the pressure fluid supplied to the percussion device, characterized in that so that the pressure fluid is supplied by a pressure-controlled volume flow pump, the volume flow of the pump being controlled by the pressure occurring between the feed device and the pressure reduction means; and   (iii) adjusting the ratio of the pressures of the pressure fluids to be supplied to the percussion device and the feed device, respectively, to a substantially constant value by a pressure control means connected in series with the feed device.   
     
     
       2. A method of controlling the percussion power of a percussion device according to claim 1 comprising the further step (iv) of maintaining the ratio of percussion pressure to feed pressure substantially constant by adjusting the percussion pressure correspondingly to the feed pressure, so that the level of percussion power is directly proportional to that of the feed pressure. 
     
     
       3. A method of controlling the percussion power of a percussion device according to claim 1 wherein the volume flow of step (ii) of the pressure fluid entering the percussion machinery is proportional to said percussion power. 
     
     
       4. An arrangement for controlling the percussion power of a percussion device in a pressure fluid operated rock drilling apparatus, comprising; a pressure fluid pump, a percussion device and a feed device, supply lines of the percussion device and of the feed device connected to a pressure line from the pump, and at least one pressure reduction means connected between the pressure line of the pump and the feed device to reduce the pressure of the pressure fluid to be supplied to the feed device to a value lower than the pressure of the pressure line of the pump;   said pump comprising a pressure-controlled volume flow pump, a control pressure line from the pump connected to the supply line of the feed device between the pressure reduction means and the feed device; and   at least one pressure control means connected to the supply line of the feed device in series with it to keep the pressure of the pressure fluid to be supplied into the percussion device at a substantially constant ratio relative to the pressure occurring in the supply line of the feed device.   
     
     
       5. An arrangement according to claim 4, wherein said pressure reduction means is a throttle. 
     
     
       6. An arrangement according to claim 4, wherein said pressure control means is an adjustable pressure-difference valve connected between the throttle and the feed device. 
     
     
       7. An arrangement according to claim 6, wherein said control pressure line of the pump is connected between the pressure-difference valve and the feed device. 
     
     
       8. An arrangement according to claim 6, wherein said control pressure line of the pump is connected between the pressure-difference valve, the arrangement further comprising an adjustable pressure relief valve connected to said control pressure line of the pump and limiting the pressure of said control line, and thus the pressure of the pressure fluid to be supplied to the percussion device, to a predetermined maximum value. 
     
     
       9. An arrangement according to claim 8, wherein said control means for the pressure-difference valve and the pressure relief valve are connected together to be controlled simultaneously so that when adjusting the maximum pressure of the pressure fluid to be supplied to the percussion device, the pressure-difference valve is correspondingly adjusted so that the ratio of the pressure of the pressure fluid to be supplied to the percussion device and that of the pressure fluid to be supplied to the feed device remains substantially constant for a particular adjustment. 
     
     
       10. An arrangement for controlling the percussion power of a percussion device according to claim 2 wherein said feed device is a pressure fluid cylinder. 
     
     
       11. An arrangement for controlling the percussion power of a percussion device according to claim 2 further comprising means for establishing a pressure differential between the feed device and the control line of the pump and the percussion device. 
     
     
       12. An arrangement for controlling the percussion power of a percussion device according to claim 11 wherein said means for establishing the pressure differential between the feed device and the control line of the pump and percussion device comprises means for establishing a pressure differential that is proportional to the pressure lost by the pressure control means.